1. Field of the Invention
The present invention relates to a self-propelled work machine such as an earthmoving machine or an industrial tractor including various operation modes, and more particularly, to a work machine capable of expanding operation speed of an operation machine and running speed of the work machine up to a desired speed range not within the above operation modes in accordance with variation in kinds of operation or operation conditions under various operation modes.
2. Description of the Related Art
Conventionally, various work machines for construction or civil engineering are known. This kind of work machine includes a revolving body mounted on a running body such that the revolving body can revolve around a vertical axis, and the revolving body has operation machines such as a main boom, a stick boom, and a bucket. In this work machine, pressure oil delivered from a variable displacement pump driven by an engine is switched by a plurality of direction-switching valves, thereby selectively supplying the pressure oil to actuators of a main boom cylinder, a stick boom cylinder, a bucket cylinder, a revolving motor and a running motor to drive each operation machine or allow the work machine run.
Japanese Patent Publication No.2863599 discloses one example of the work machine having this operation machine. A hydraulic operation machine disclosed in this publication comprises an acceleration lever for setting the number of revolution of an engine, a revolution speed instruction transmitter for detecting an operation amount of acceleration lever to output an engine revolution speed instruction signal in accordance with the operation amount, engine revolution speed setting means for increasing or reducing the engine revolution speed, flow rate adjusting means for increasing or reducing a pump flow rate of a variable displacement pump, a relief valve for setting a discharge-side maximum operation pressure of the pump, and relief pressure setting means for setting a maximum pressure of the pressure oil introduced into the operation machine actuator.
Further, this hydraulic operation machine includes, in addition to a combination of operation power and operation speed of an actuator required during normal operation, operation mode selecting means in which various operation modes such as an operation mode for operating the actuator at high speed, an operation mode for carrying out precise operation are previously stored so that these modes can freely be selected.
If an operator selects a desired operation mode using the operation mode selecting means in accordance with the kind of operation to be carried out or operation condition, the operation mode selecting means selects at least one of a maximum engine revolution number of the engine, a maximum delivery flow rate of the pump, a maximum pressure of pressure oil to be introduced into the actuator for the operation machine which are previously stored for each of the selected operation mode, and the selected value is output to a controller as an operation mode instruction signal.
The controller receives an operation instruction signal from the operation mode selecting means and an engine revolution speed instruction signal from the revolution speed instruction transmitter, lower one of the operation mode instruction signal and the engine revolution speed instruction signal is selected as the maximum engine revolution number, and an instruction signal is output to the engine revolution speed setting means. At the same time, an instruction signal is output to the flow rate adjusting means of the pump based on the operation mode instruction signal, and an instruction signal is output to the relief valve and the relief pressure setting means.
In this manner, the instruction signal is output to the flow rate adjusting means and the engine revolution speed setting means so that the operation speed of the actuator which is to be operated based on the instruction signal from the controller is not excessively great or small so as to control the delivery oil amount of the variable displacement pump. At the same time, an instruction signal is output to the relief valve and the relief pressure setting means so that the operation power of the actuator is not excessively great or small, thereby controlling the pressure of the pressure oil flowing into the actuator.
According to this conventional hydraulic operation machine, the flow rate and the maximum pressure of the pressure oil flowing into the actuator is automatically limited by the revolution speed setting means, the flow rate adjusting means, the relief pressure setting means and the like. Therefore, it is described in the above patent publication that the operation speed and operation force of the operation machine most suitable for the kind of operation and the operation condition of the selected operation mode can be obtained.
Further, it is described in the above patent publication that since it is possible to also avoid the maximum revolution of the engine which is needless for a certain operation mode, various operations can be smoothly and easily carried out with the same machine and thus, the frequency of misoperation is low, the machine is not brought into a driving state which is harmful for another object or which shortens life of the machine, which leads to a quiet operation, and this is effective for both a skilled operator or a unskilled operator.
In the hydraulic operation machine disclosed in the above patent publication, various suitable operation modes corresponding to various driving and operation conditions are previously assumed, and these modes are stored in the operation mode selecting means. However, these operation modes are selected by an operator by his or her sense or judgement immediately before the operation is started when the kind of operation or operation condition is changed and the operation environment is changed. For example, under a condition in which various variations including variation in weather, a range of operation and a problem whether an obstruction exists or not are caused, correspondence of the set operation mode does not always meet with the actual condition under which the operation is to be carried out.
Further, the controller only uniformly outputs an instruction signal which is consistent with the set operation mode to the engine, the variable displacement pump, the relief valve and the like. If a certain operation mode is once set, even if the kind of executed operation or operation condition is changed, it is not possible to change the set operation speed or the set operation pressure of the operation machine in the operation mode. Therefore, even if the previously set operation mode is not suitable for the actual operation condition, or even if the previously set operation mode is not a mode corresponding to the skill of the operator, the operation in a range of this operation mode is forced to be carried out, and this is prone to lower the operation efficiency.
The present invention has been accomplished to solve the above conventional problems, and it is a particular object of the invention to provide various work machines in which safety of operation and operation efficiency can be enhanced in accordance with variation in the kind of operation and operation condition when operation is carried out based on a previously set operation mode of an operation machine, and operation speed of the operation machine or running speed of the work machine can finely be adjusted.
According to a first aspect of the invention, there is provided a work machine comprising mode switching means of operation modes of one or more operation machines, wherein the work machine further comprises speed finely-adjusting means capable of finely adjusting an operation speed and/or a running speed to be out of a range of these speeds set in each mode by a manual operation.
According to the invention, if an operator selected one of the operation modes of one or more operation machines by the mode switching means, the actuator of the operation machine or the running motor is automatically controlled by a signal output from the mode switching means. If the operator further operates the speed finely-adjusting means after the operation mode of the operation machine was initialized, the operation speed of the actuator or the driving speed of the running motor in the current operation mode is extended to a value out of the set speed range of the current operation mode by a signal output from the speed finely-adjusting means. A width of extension at that time slightly exceeds a set speed range of the basic operation mode, and the operation of the operation machine can finely be adjusted in a region out from the set speed range of the operation mode by the operation of the speed finely-adjusting means.
Therefore, even under an environment in which operation range is changed or an obstruction may exist, it is possible to effectively obtain optimal operation mode of the operation machine suitable for the kind of operation which is carried out and operation condition and skill of an operator, stable running performance and operability of the operation machine can be realized, and the operation efficiency is remarkably enhanced.
Preferably, a driving circuit for one or more operation machines and a running motor includes flow rate adjusting means, the flow rate adjusting means is operated by a signal output through the speed finely-adjusting means, and a flow rate in the driving circuit is adjusted.
In this invention, when the speeds of the one or more operation machines and the running motor which are automatically controlled based on the operation mode are to be further adjusted, flow rate adjusting means disposed in each of driving circuits of an actuator of the operation machine, the running motor, a revolving motor and the like are selectively operated by a signal output through the speed finely-adjusting means which is operated by the operator, thereby increasing or reducing the flow rate of the pressure oil supplied to the actuator. A certain actuator can smoothly be adjusted without exerting an effect on other actuator.
Further preferably, the flow rate adjusting means includes various main valves, and an opening area of each of various main valves is adjusted by a signal sent through the flow rate adjusting means.
In this invention, the stroke of the spool of the main valve is finely adjusted by the speed finely-adjusting means to increase or reduce the flow rate of the pressure oil supplied to the actuator, and the speeds of the operation machine and the running motor are changed. For example, the operation speed of the operation machine is set based on the operation mode of the operation machine which was initialized, and when it is necessary to further reduce the operation speed, the speed finely-adjusting means is operated to reduce the opening area of the main valve to a value smaller than that when the speed is within the range of the selected operation mode, the flow rate of the pressure oil supplied to the actuator is reduced, and the speed of the operation machine can further be reduced to a value smaller than the lower limit speed of the selected operation mode.